Featured Research

Collapsing Star Gives Birth to a Black Hole

Posted: July 28, 2017

Illustration of a failing supernova giving birth to a black hole.

OU Professor Xinyu Dai, in collaborarion with a group of Astronomers, has watched as a massive, dying star was likely reborn as a black hole. It took the combined power of the Large Binocular Telescope (LBT), and NASA's Hubble and Spitzer space telescopes to go looking for remnants of the vanquished star, only to find that it disappeared out of sight. It went out with a whimper instead of a bang. The star, which was 25 times as massive as our sun, should have exploded in a very bright supernova. Instead, it fizzled out—and then left behind a black hole. As many as 30 percent of such stars, it seems, may quietly collapse into black holes — no supernova required. The work was recently published in the Monthly Notices of the Royal Astronomical Society.

Among the galaxies they've been watching is NGC 6946, a spiral galaxy 22 million light-years away that is nicknamed the "Fireworks Galaxy" because supernovae frequently happen there — indeed, SN 2017eaw, discovered on May 14th, is shining near maximum brightness now. Starting in 2009, one particular star, named N6946-BH1, began to brighten weakly. By 2015, it appeared to have winked out of existence. After the LBT survey for failed supernovas turned up the star, astronomers aimed the Hubble and Spitzer space telescopes to see if it was still there but merely dimmed. They also used Spitzer to search for any infrared radiation emanating from the spot. That would have been a sign that the star was still present, but perhaps just hidden behind a dust cloud.

All the tests came up negative. The star was no longer there. By a careful process of elimination, the researchers eventually concluded that the star must have become a black hole. It's too early in the project to know for sure how often stars experience massive fails, but Scott Adams, a former Ohio State student who recently earned his Ph.D. doing this work, was able to make a preliminary estimate.